Page 18 - Curriculum Visions Dynamic Book

Sodium and the human body
Sodium, in the form of salt, is present in many of the foods we eat. In general, if we eat animal products such as milk, fats or meat, we do not need to add extra salt to any of our foods.
Why is it, then, that our tongues have special areas that detect salt? And why do we like the taste of salt so much? The answer lies in part in the role of osmosis.
Salt in the blood
Biologically, blood is a saline solution, that is, it
is mostly water with salt dissolved in it. The red blood cells, present in the saline solution, which give blood its familiar appearance, are a relatively small part of the liquid we call blood.
The main use of salt in the body is to control the way water is taken up and expelled from the organs. Salt is also important in making sure that nerve cells work properly.
Blood contains more salt and less water than digested food, water, and other energy-giving molecules. These are then are attracted towards the blood as it courses through vessels that
line the digestive tract. The blood then carries nutrients to all the cells in the body.
 Oral rehydration salts
In some circumstances, such as when the body is affected by a disease that causes diarrhoea, large amounts of fluids are lost. The body does not have time to filter out the salts it needs and these are carried away with the fluids. To help people to recover from these illnesses, the body needs not just fluids, but also a balanced range of salts, so that it can quickly regain the ability to absorb nutrients and energy from food.
To help the body regain the salts, patients are given oral rehydration therapy, consisting of a balanced mixture of salts dissolved in water. This cheap and effective cure saves millions of lives each year.
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Saline drip for emergencies
When people lose blood, the first thing that a doctor does is to give them an intravenous injection of water and salt, known as a saline drip. A saline drip contains no blood cells, so it does not have to be matched to the blood group and can be used on anybody.
Using a saline drip will ensure that there is enough liquid in the bloodstream until alternative supplies of matching blood can be found.